Introduce <elf-initfini.h> and ELF_INITFINI for all architectures

This supersedes the init_array sysdeps directory.  It allows us to
check for ELF_INITFINI in both C and assembler code, and skip DT_INIT
and DT_FINI processing completely on newer architectures.

A new header file is needed because <dl-machine.h> is incompatible
with assembler code.  <sysdep.h> is compatible with assembler code,
but it cannot be included in all assembler files because on some
architectures, it redefines register names, and some assembler files
conflict with that.

<elf-initfini.h> is replicated for legacy architectures which need
DT_INIT/DT_FINI support.  New architectures follow the generic default
and disable it.

1 files changed, 19 insertions, 0 deletions

diff --git a/sysdeps/generic/crtn.S b/sysdeps/generic/crtn.S
new file mode 100644
index 0000000000..d92b07dd0b
--- /dev/null
+++ b/sysdeps/generic/crtn.S
@@ -0,0 +1,19 @@
+/* Dummy crtn file.
+
+   In this configuration, crti.o and crtn.o are both empty because the
+   .init_array/.fini_array sections are used exclusively.
+
+   Older ports cannot use this because even if the linker used to
+   build libc itself has .init_array support, we don't want to produce
+   a crt[in].o that presume a linker that new will be used to link
+   other things later.
+
+   But new configurations without compatibility concerns for
+   toolchains without .init_array support can use this to avoid the
+   superfluous .init and .fini boilerplate code.  */
+
+#include <elf-initfini.h>
+
+#if ELF_INITFINI
+# error Cannot use genetric crtn.S because it lacks _fini code
+#endif